This application is based on Application No. 2000-276403, filed in Japan on Sep. 12, 2000, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a stator of a dynamo-electric machine of, for example, an automotive alternator or the like, and a manufacturing method and a connecting conductor wire for the stator, and a manufacturing method for the connecting conductor wire.
2. Description of the Related Art
Hitherto, a variety of types of electric equipment use diverse types of conductor wires according to individual applications. In some applications, conductor wires are joined together for use.
In such a case, the end portions of conductor wires to be joined are arranged properly, and insulating films formed on the end portions are removed. Then, the stripped end portions are joined, and a new insulating resin is applied to the stripped portions that include the joined portion to complete the joining process of the conductor wires.
Such a joining method, however, has been posing a problem in that the entire distal ends of conductor wires to be joined are melted, requiring high calorie for joining them. There has been another problem in that an increase in heat gain during the joining process causes an increase in the temperature around the end portions of the conductor wires and deteriorates insulating films, with resultant deteriorated insulating properties.
To solve the aforesaid problems, there has been proposed in, for example, Japanese Unexamined Patent Application Publication No. 2000-164043, a conductor wire structure in which the end portions of the conductor wires to be joined are partly cut off to reduce cross-sectional areas of the wires so as to reduce a heat gain during a joining process.
FIG. 19 is a process chart illustrating a conventional process for connecting conductor wires disclosed in, for example, Japanese Unexamined Patent Application Publication No. 2000-164043.
In the conventional process for connecting conductor wires, two conductor wires 100 to be joined are first prepared, and insulating films 116 are removed from the areas around the end portions of the conductor wires 100 (step 1). Then, end portions 112 of the conductor wires 100 from which the insulating films 116 have been removed are partly cut off as illustrated to form cut portions 114 (step 2). Substantially half of the round section of each of the end portions 112 of the conductor wires 100 are cut off by forming the cut portion 114. The cross-sectional area is substantially reduced to half the area connected to the end portion 112. Then, the two conductor wires 100 are disposed in parallel to each other, with their cut portions 114 facing outward, the end portions 112 being arranged properly. Subsequently, the end portions 112 are joined by, for example, tungsten-inert-gas (TIG) welding (step 3). Finally, an insulating resin 120 is newly applied to a joined portion 118 and the area from which the insulating films 116 have been removed (step 4), thus completing the joining process of the two conductor wires 100.
As described above, in the conventional structure of the conductor wire, the end portion 112 of the conductor wire 100 is partly cut off to reduce the conductor sectional area, so that the insulating film 116 of the conductor wire 100 around the cut portion 114 is inevitably damaged. For this reason, after joining the end portions 112 of the conductor wires 100, the insulating resin 120 must be applied to a wide area including the joined portion 118. This has been posing a problem of poor working efficiency and an increase in the volume of the insulating resin 120, causing the joined portion of the conductor wires to bulge out.
The following will describe a case where the conductor wires having the conventional structure are applied to a stator 121 of an alternator.
As shown in FIG. 20, the stator 121 is equipped with a stator iron core 122 and a stator winding 123 composed of conductor wires 124 threaded through slots 122a of the stator iron core 122. In a coil end group 123a of the stator winding 123, joined portions 125, each being composed of welded end portions of two conductor wires 124 with an insulating resin 120 applied thereto, are aligned in two layers adjacently in one row in the radial direction on an end surface of the stator iron core 122, being disposed in two rows in the circumferential direction.
Since the end portions of the conductor wires 124 are partly cut off as in the case of the conductor wires 100 described above, the insulating film 116 around the cut-off area is damaged, causing the conductors to be exposed. The joined parts of the end portions of the conductor wires 124 are aligned adjacently in one row in the radial direction on the end surface of the stator iron core 122, being disposed in two rows in the circumferential direction. Hence, welded portions of the end portions of the conductor wires 124 aligned adjacently in the radial direction are likely to develop short-circuiting. If the insulating resin 120 is applied with a welded portion short-circuited, then the yield of the stator 121 will be reduced.
To prevent the yield from lowering, an inspection for checking the welded portions of the end portions of the conductor wires 124 for a short circuit is performed prior to the application of the insulating resin 120. A rejected workpiece must be subjected to a step for locating a short-circuited spot, then the short circuit must be corrected by separating the short-circuited welded portions in the radial direction by hand.
It is extremely difficult to locate a short-circuited spot. The step for correcting a short circuit requires the manufacturing line of stators be stopped, and is implemented by hand, leading to significantly reduced productivity and increased cost.
Furthermore, since the insulating resin 120 must be applied to a large sectional area in the vicinity of the cut portion, the joined portion 125 bulges out, adding to a radial dimension and a circumferential dimension. This prevents the stator 121 from being made smaller, and adversely affects the multi-row configuration of the joined portions 125.
The present invention has been made with a view toward solving the above problems, and it is an object of the present invention to provide a stator of a dynamo-electric machine and a manufacturing method for the same, and a connecting conductor wire and a manufacturing method for the same in which an end portion of a conductor wire is plastically deformed to minimize the chances of damage to an insulating film and to reduce a cross-sectional area of the end portion thereby to reduce heat gain during a joining process and secure good insulating properties. Moreover, the occurrence of short circuits between joined portions will be structurally prevented so as to obviate the need for manual correction of short circuits that used to be necessary in the conventional art, thus allowing higher productivity and lower cost to be achieved.
To this end, according to one aspect of the present invention, there is provided a stator of a dynamo-electric machine that is equipped with a cylindrical stator iron core having a plurality of slots arranged in a circumferential direction; and a stator winding composed of a plurality of conductor wires installed in the slots, the stator winding being formed by joining end portions of the plurality of conductor wires extending out of different ones of the slots at the end surface of the stator iron core, wherein the conductor wires are formed such that a conductor sectional area of an end portion over a predetermined extent in a lengthwise direction from a distal end thereof is smaller than a conductor sectional area of a main portion, and an insulating film covers the main portion and a part of the end portion in the vicinity of the main portion; and a plurality of the conductor wires extending out of the different slots are joined with their end portions arranged properly.
In a preferred form, the end portion of each of the conductor wires is formed of a tapered portion having its conductor sectional area continuously reducing from the main portion toward the distal end thereof and a constant-sectional-area portion extending from the tapered portion toward the distal end, the conductor sectional area thereof being kept unchanged.
In another preferred form, the end portions of the conductor wires are eccentric with respect to the main portion in the vicinity of the end portion, and arranged properly so that the end portions of the conductor wires are brought close to each other before they are joined.
In yet another preferred form, the outer peripheral surface of an end portion of the conductor wire at the opposite side from its counterpart has a curved surface when the end portions of the conductor wires are arranged properly.
In still another preferred form, the end portions of the conductor wires are formed to have substantially circular cross sections.
In a further preferred form, the end portions of the conductor wires are formed to have substantially elliptical cross sections.
In another preferred form, both circumferential side surfaces of the end portions of the conductor wires are formed to have a planar shape in a radial direction.
In another preferred form, the circumferential width of the end portion of the conductor wire is set to equal to or smaller than the circumferential width of the main portion.
According to another aspect of the present invention, there is provided a manufacturing method for a stator of a dynamo-electric machine having a cylindrical stator iron core having a plurality of slots arranged in a circumferential direction; and a stator winding composed of a plurality of conductor wires installed in the slots, each of the conductor wires being formed such that a conductor sectional area of an end portion over a predetermined extent in a lengthwise direction from a distal end thereof is smaller than a conductor sectional area of a main portion, the main portion and a part of the end portion in the vicinity of the main portion being covered with an insulating film, and the stator winding being formed by joining the end portions of the plurality of conductor wires extending out of different ones of the slots at the end surface of the stator iron core, with their end portions arranged properly, the method including a step for placing a metal block between a pair of the arranged end portions of the conductor wires and an adjoining one of the conductor wires; and a step for joining the pair of the end portions of the conductor wires while pressing the pair of the arranged end portions of the conductor wires against the metal block by a first pressurizing jig.
In a preferred form, the metal block is made of copper or a copper alloy.
In another preferred form, the pair of the arranged end portions of the conductor wires are joined while binding the end portions in the circumferential direction.
In yet another preferred form, the pair of the arranged end portions of the conductor wires are joined by heating them by a non-contact heating source.
In a further preferred form, the non-contact heating source uses an arc or plasma; the first pressurizing jig is metallic; the pair of the arranged end portions of the conductor wires are pressed against the metal block by the first pressurizing jig; the conductor wires adjacent to the pair of the arranged end portions of the conductor wires are also pressed against the metal block by a second pressurizing jig made of metal; and an output terminal of a power source for generating the non-contact heating source is connected to the first and second pressurizing jigs to join the pair of the arranged end portions of the conductor wires.
According to yet another aspect of the present invention, there is provided a manufacturing method for a stator of a dynamo-electric machine having a cylindrical stator iron core having a plurality of slots arranged in a circumferential direction; and a stator winding composed of a plurality of conductor wires installed in the slots, each of the conductor wires being formed such that a conductor sectional area of an end portion over a predetermined extent in a lengthwise direction from a distal end thereof is smaller than a conductor sectional area of a main portion, the main portion and a part of the end portion in the vicinity of the main portion being covered with an insulating film, and the stator winding being formed by joining the end portions of the plurality of conductor wires extending out of different ones of the slots at the end surface of the stator iron core, with their end portions arranged properly, the method including a step for plastically deforming a conductor wire rod, which has been entirely covered with the insulating film, for a predetermined extent thereof in a lengthwise direction from the distal end thereof so as to make the conductor sectional area of the end portion smaller than the conductor sectional area of the main portion; and a step for removing the insulating film from the end portion such that the insulating film remains on a part of the end portion in the vicinity of the main portion to complete the conductor wire.
According to yet another aspect of the present invention, there is provided a connecting conductor wire that is formed such that a conductor sectional area of an end portion over a predetermined extent in a lengthwise direction from a distal end thereof is smaller than a conductor sectional area of a main portion, wherein the main portion and a part of the end portion in the vicinity of the main portion are covered with an insulating film.
In a preferred form, the end portion is formed of a tapered portion having its conductor sectional area continuously reducing from the main portion toward the distal end thereof and a constant-sectional-area portion extending from the tapered portion toward the distal end, the conductor sectional area thereof being kept unchanged.
According to a further aspect of the present invention, there is provided a manufacturing method for a connecting conductor wire, including a step for plastically deforming a conductor wire, which has been covered with the insulating film, for a predetermined extent thereof in a lengthwise direction from the distal end thereof so as to make the conductor sectional area of the end portion smaller than the conductor sectional area of the main portion; and a step for removing the insulating film from the end portion such that the insulating film remains on a part of the end portion in the vicinity of the main portion.